Such an electronic thermometer has been known that can correctly measure a body temperature by determining whether a human body is in contact with a temperature sensor or not.
As such a kind of electronic thermometer, for example, a patent document 1 has disclosed an electronic thermometer that utilizes, for sensing a contact with a human body, a switch, a contact resistance, an electrostatic capacity, a humidity, a pressure (contact), a temperature comparison, a change in temperature and the like.
However, in the method that senses a contact state by determining whether a measurement target portion has pushed a switch or not, when a probe is in a contact position, or in a method that senses a contact state depending on a contact that occurs between two contact points owing to deformation of the probe caused by a pushing force of the measurement target portion; a detection error may occur due to the contact with or pushing by a portion other than the human body or by a portion other than the measurement target portion.
Also, there are methods in which a contact state is sensed when two contact points exposed on a surface of a probe simultaneously come into contact with a measurement target portion and are electrically connected together through the measurement target portion, or the contact state is sensed when a measurement target portion comes into contact with a surface portion of a probe functioning as an electrode of a capacitor or a dielectric to change an electrostatic capacity of the capacitor. In these methods, since a metal portion exposed on the surface of the probe comes into contact with a human body, electricity directly flows through the human body so that current leakage of the like may adversely affect the human body. Also, it is difficult to employ antistatic measures because the electrode is arranged on the probe surface, and the static electricity may break internal parts such as a CPU. In a structure that has a protruding switch or an electrode near the probe, a user may feel uncomfortable when the switch or electrode touches the human body.    Patent Document 1: Japanese Patent National Publication No. 61-500038